Support external RPC servers via IPC

[cryptocode]

Remaining

• Add tests (write an IPC client class for this)
• Document the framing format in the code
• Add ipc logging option with upgrade path
• Config upgrade path (merge Error type and config handling #1416 first)
  After reviewing/testing, will also add this:
• Replace boost::bind with lambdas
• Utilize the new nano::timer class
• Introduce session id for improved logging

This adds support for external RPC servers that communicate with the node via IPC (currently domain sockets and tcp).

Using external web servers can benefit service scalability and security. IPC connections are persistent, which should reduce time_wait (file descriptor exhaustion) issues on busy servers.

The internal RPC server can thus be disabled in the config, yet have the functionality exposed via IPC. The JSON format is exactly the same as the internal server - clients only need to change URL.

A proof-of-concept REST server in Go is available at https://github.com/nanocurrency/rpc-go.

The IPC gateway allows for other message payloads like protobuf (there's a PR for protobuf which would need some work to work with this PR)

Technically, the IPC gateway defines a simple framing format with an encoding flag. In this case, the encoding is 1 (json rpc) which expects a payload of 32-bit big-endian size + json, which is also the case for the response. The json payload is forwarded to the node's existing RPC action handler. More info will be added to the wiki.

Configuration

To test the rpc-go server, enable either tcp or local ipc in the node config. Do the corresponding change in rpc-go's config.json (which uses domain sockets by default)

The rpc_enable flag can still be active, to access the current RPC server.

[cryptocode]

@meltingice is working on an IPC lib and gRPC interface based on this PR

https://github.com/meltingice/nano-ipc-js
https://github.com/meltingice/nano-grpc

[meltingice]

FYI if anyone else runs into this issue... after updating to the latest commit on this PR, the node could no longer deserialize the config. It was missing the node.logging.timing config option, which didn't get added by a config upgrade. Works fine once added. Default is false.

[cryptocode]

Yeah, the timing upgrade was recently added to master

[meltingice]

I am getting an exception that's crashing the node when attempting to call account_representative_set via IPC on an unopened account. The crash does not happen when attempting the same call via the HTTP RPC.

The call I'm making is:

{
  "action": "account_representative_set",
  "wallet": "523325FC5B61CB450035B32AAE11FE7F02BEB5D3F736EF59FC3C7B0FAD35C46C",
  "account": "xrb_118fd6yj4mzc17k3q9ugygdqwj8cxqia8hgrxijb1efahsmnwzk8qs3foxnt",
  "representative": "xrb_1x7biz69cem95oo7gxkrw6kzhfywq4x5dupw4z1bdzkb74dk9kpxwzjbdhhs"
}

And the crash message is:

libc++abi.dylib: terminating with uncaught exception of type std::__1::bad_weak_ptr: bad_weak_ptr
[1]    11184 abort      ./nano_node --daemon --data_path=/Users/ryanlefevre/RaiBlocks/

I'm running this node on macOS 10.14.2.

[cryptocode]

@meltingice thanks for the report. This seems to be related to action handlers with asynchronous responses (wallet->change_async in this case). I'll look into it.

[meltingice]

Just tested and appears to be fixed now. Thanks @cryptocode!

[clemahieu]

Looks great!

[meltingice]

The JS client library has been updated to match the preamble changes. https://www.npmjs.com/package/nano-ipc